Semiconductor devices are usually fabricated on wafers. Typically, hundreds of identical devices are fabricated on the same wafer. The devices on the wafer are cut into single pieces. Each piece is individually packaged and becomes a chip such as a memory device or a microprocessor.
At the end of fabrication process, the devices on the wafer are tested for many electrical functions. Electrical failures are major contributors to the yield loss in semiconductor device fabrication. To improve the yield, failure analysis is often performed on test results to help correct the failures. However, the test results accumulate over time and may be massive and complex, causing the failure analysis to become difficult and time consuming. Furthermore, the test results may incorporate multiple failure mechanisms, which may be very hard to decouple.